A hybrid between a domestic duck (male) and a domestic goose (female) acquired by the Zoological Gardens, Copenhagen superficially resembled a duck, but by a closer examination it was showed that morphologically and ethologically it showed characters of both duck and goose. Although it is a male it has never shown any sexual activity. I therefore tried to activate it by hormone injections. Treatment with gonadotropic hormones and with sexual hormone were both ineffectual. Therefore I conclude that this bird does not have the nervous mechanisms underlying the sexual patterns, because it is known that castrated male birds and young male birds show sexual activity when treated with hormones.